U.S. patent application number 12/360567 was filed with the patent office on 2009-08-27 for organic/inorganic hybrid thin film passivation layer for blocking moisture/oxygen transmission and improving gas barrier property.
This patent application is currently assigned to Korea Institute of Science and Technology. Invention is credited to June Whan Choi, Jai Kyeong Kim, Joo-Won Lee, Jae-Hyun Lim, Dae-Seok Na, Jung Soo Park.
Application Number | 20090215279 12/360567 |
Document ID | / |
Family ID | 40998747 |
Filed Date | 2009-08-27 |
United States Patent
Application |
20090215279 |
Kind Code |
A1 |
Kim; Jai Kyeong ; et
al. |
August 27, 2009 |
ORGANIC/INORGANIC HYBRID THIN FILM PASSIVATION LAYER FOR BLOCKING
MOISTURE/OXYGEN TRANSMISSION AND IMPROVING GAS BARRIER PROPERTY
Abstract
The present invention relates to an organic/inorganic hybrid
thin film passivation layer comprising an organic polymer
passivation layer prepared by a UV/ozone curing process and an
inorganic thin film passivation layer for blocking moisture and
oxygen transmission of an organic electronic device fabricated on a
substrate and improving gas barrier property of a plastic
substrate; and a fabrication method thereof. Since the
organic/inorganic hybrid thin film passivation layer of the present
invention converts the surface polarity of an organic polymer
passivation layer into hydrophilic by using the UV/ozone curing
process, it can improve the adhesion strength between the
passivation layer interfaces, increase the light transmission rate
due to surface planarization of the organic polymer passivation
layer, and enhance gas barrier property by effectively blocking
moisture and oxygen transmission.
Inventors: |
Kim; Jai Kyeong; (Seoul,
KR) ; Park; Jung Soo; (Seoul, KR) ; Choi; June
Whan; (Seoul, KR) ; Na; Dae-Seok; (Daegu,
KR) ; Lim; Jae-Hyun; (Seoul, KR) ; Lee;
Joo-Won; (Seoul, KR) |
Correspondence
Address: |
JONES DAY
222 EAST 41ST ST
NEW YORK
NY
10017
US
|
Assignee: |
Korea Institute of Science and
Technology
|
Family ID: |
40998747 |
Appl. No.: |
12/360567 |
Filed: |
January 27, 2009 |
Current U.S.
Class: |
438/763 ;
257/E21.24 |
Current CPC
Class: |
Y10T 428/31511 20150401;
Y10T 428/31855 20150401; H01L 51/448 20130101; Y10T 428/31721
20150401; Y02E 10/549 20130101; Y10T 428/31504 20150401; H01L
51/5256 20130101 |
Class at
Publication: |
438/763 ;
257/E21.24 |
International
Class: |
H01L 21/31 20060101
H01L021/31 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 25, 2008 |
KR |
10-2008-0016888 |
Claims
1. A method of fabricating an organic/inorganic hybrid thin film
passivation layer for blocking moisture and oxygen transmission and
improving gas barrier property comprising: coating an organic
electronic device fabricated on a substrate or on a top or both the
top and bottom of a plastic substrate with a photocurable polymer;
curing the coated photocurable polymer by a UV/ozone (UV/O.sub.3)
process to form an organic polymer passivation layer; and
depositing a nanocomposite material containing at least two
inorganic materials on the organic polymer passivation layer to
form an inorganic thin film passivation layer.
2. The method according to claim 1, wherein the photocurable
polymer is selected from the group consisting of epoxy resins,
acrylate resins, thermocurable polyimide and polyethylene.
3. The method according to claim 1, wherein the photocurable
polymer is coated by spin coating, screen printing, bar coating,
inkjet printing, or dipping.
4. The method according to claim 1, wherein the coated photocurable
polymer has a thickness of 0.1 to 10 .mu.m.
5. The method according to claim 1, wherein the organic electronic
device is fabricated on a flexible substrate or a glass
substrate.
6. The method according to claim 5, wherein the flexible substrate
is made of a material selected from the group consisting of
polyethylene terephthalate (PET), polymethyl methacrylate (PMMA),
polycarbonate (PC), and polyethylene sulfone (PES).
7. The method according to claim 1, wherein the plastic substrate
is made of a material selected from the group consisting of
polyethersulfone, polycarbonate, polyethylene terephthalate and
polyimide.
8. The method according to claim 1, wherein the UV/ozone process
includes pre-curing, UV/ozone irradiation, and heat curing.
9. The method according to claim 8, wherein the pre-curing is
carried out by treating the photocurable polymer at a temperature
of 70 to 90.quadrature. for 2 to 5 min.
10. The method according to claim 8, wherein the UV/ozone
irradiation is carried out by irradiating the pre-cured
photocurable polymer with a light source having an energy of 2400
to 3000 mJ/cm.sup.2 at a wavelength range of 170 to 200 nm for 1 to
7 min to degrade oxygen molecules into oxygen atoms, followed by
irradiation with a light source having an energy of 2400 to 2700
mJ/cm.sup.2 at a wavelength range of 240 to 270 nm for 1 to 7 min
to generate ozone from the oxygen atoms.
11. The method according to claim 8, wherein the heat curing is
carried out by treating the UV/ozone irradiated photocurable
polymer at a temperature of 100 to 120.quadrature. for 1 to 2
hr.
12. The method according to claim 1, wherein the nanocomposite
material is a mixture containing at least two inorganic materials
selected from the group consisting of metal oxides, non-metal
oxides, nitrides, and salts.
13. The method according to claim 12, wherein the nanocomposite
material is a mixture containing at least two inorganic materials
selected from the group consisting of aluminum oxides, silicone
oxides, silicone nitrides, silicone oxidenitrides, magnesium
oxides, indium oxides, and magnesium fluorides.
14. The method according to claim 12, wherein the depositing of the
nanocomposite material is carried out by using an electron beam
evaporator, a sputter, physical vapor deposition (PVD), chemical
vapor deposition (CVD) or atomic layer deposition (ALD).
15. The method according to claim 1, wherein the deposited
nanocomposite material has a thickness of 0.1 to 0.5 .mu.m.
16. The method according to claim 1, wherein the coating, the
curing, and the depositing are repeatedly carried out in order, so
as to form a pair of the organic polymer passivation layer and
inorganic thin film passivation layer in a multilayer laminate
structure.
17. The method according to claim 1, wherein the depositing a
nanocomposite material is carried out prior to the coating an
organic electronic device and the curing the coated photocurable
polymer, so as to form an inorganic thin film passivation layer
before the deposition of the organic polymer passivation layer.
18. The method according to claim 17, wherein the coating, the
curing, and the depositing are repeatedly carried out in order, so
as to form a pair of the inorganic thin film passivation layer and
organic polymer passivation layer in a multilayer laminate
structure.
19. An organic/inorganic hybrid thin film passivation layer for
blocking oxygen and moisture transmission of an organic electronic
device fabricated on a substrate and improving gas barrier property
of a plastic substrate, which comprises an organic polymer
passivation layer and an inorganic thin film passivation layer and
has a vertical laminate structure of the organic polymer
passivation layer and inorganic thin film passivation layer.
20. The organic/inorganic hybrid thin film passivation layer
according to claim 19, wherein the hybrid thin film passivation
layer has a multilayer laminate structure by repeatedly forming one
pair of the organic polymer passivation layer and inorganic thin
film passivation layer.
21. The organic/inorganic hybrid thin film passivation layer
according to claim 19, wherein the hybrid thin film passivation
layer has a vertical laminate structure of the inorganic thin film
passivation layer deposited on the organic polymer passivation
layer or the organic polymer passivation layer deposited on the
inorganic thin film passivation layer.
Description
[0001] The present application claims priority from Korean Patent
Application No. 10-2008-16888, filed Feb. 25, 2008, the subject
matter of which is incorporated herein by reference in its
entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to an organic/inorganic hybrid
thin film passivation layer for blocking moisture and oxygen
transmission of an organic electronic device fabricated on a
substrate and improving the gas barrier property of a plastic
substrate, and a fabrication method thereof.
BACKGROUND OF THE INVENTION
[0003] Organic electronic devices, such as organic light emitting
diodes (OLEDs), organic thin-film transistors (OTFTs), solar cells,
and other organic material-containing devices, have been attracting
a great deal of interest as the devices of the next generation. For
such organic electronic devices to be commercialized, high quality
passivation layers need to be developed in order to ensure the
reliability of the device. The reliability of a device is directly
related to the lifetime of the device. Most organic electronic
devices that use organic materials are problematic in that they
degrade easily by moisture, oxygen, and light existing in the
atmosphere and they show very low durability against heat, where
their lifetime decreases with a rise in temperature. Accordingly,
various methods for blocking the degradation and deterioration of
organic materials by moisture and oxygen are being developed.
[0004] Among those methods, research on passivation layers for
OLEDs has been actively underway. Korean Patent Publication No.
2002-22250 discloses a method of protecting a device by covering
its surface with a metal cap or a glass cap in a structure, as
illustrated in FIG. 1. In particular, FIG. 1 shows a structure of a
prior art organic electroluminescence device, including an anode
glass substrate 1, a hole injection layer 2, a hole transfer layer
3, a light emitting layer 4, an electron transfer layer 5, an
electron injection layer 6 and a cathode electrode 7, whose surface
is covered with a steel use stainless can or a glass lid 9
containing a humectant 8 and sealed with a sealing agent, such as
photocurable epoxy. However, since the method is incapable of
completely blocking moisture and oxygen transmission after the
fabrication of an organic device, there is an urgent need to
establish complementary measures. Further, in case of a large area
device (30 inches or more), limitations exist with respect to
consistent processing schemes and application of the device.
[0005] Korean Patent Publication No. 1999-49287 discloses a method
of applying ceramic materials, such as Al.sub.2O.sub.3, MgO, BeO,
SiC, TiO.sub.2, Si.sub.3N.sub.4, SiO.sub.2 and the like, to a
passivation layer. However, the method has several disadvantages in
that a high temperature is required for carrying out the process
and it is difficult to expect properties that are better than the
physical properties of the ceramic materials themselves. As
illustrated in FIG. 2, Korean Patent No. 540179 discloses a method
of fabricating an organic electroluminescence device having an
inorganic composite thin layer 11 containing a mixture of SiO.sub.2
and MgO at a constant ratio as a passivation layer, where the
inorganic composite thin layer is deposited on the surface of the
device. While such a method is capable of lowering the water vapor
transmission rate (WVTR) and oxygen transmission rate (OTR) by
applying a single inorganic thin film passivation layer to a
conventional organic electronic device, the method is problematic
in that it is difficult to form a uniform layer and that there is a
risk of lower uniformity against moisture and oxygen resistance due
to the weak interfacial adhesion strength, which also results in
surface light scattering and the deterioration in light
transmission.
[0006] Meanwhile, plastic substrates require characteristics, such
as low profile/small form factor, impact resistance, low thermal
expansion rate, and high gas barrier property. The primary issue
with applying plastic substrates to display and organic electronic
devices is developing a technique for improving the gas barrier
property so as to block the transmission of atmospheric gas, such
as moisture and oxygen. Plastic substrates made of polymer resin
have the advantage of being flexible, but they are problematic in
that it is easy for gases, such as moisture and oxygen, to
penetrate thereinto because of their inherent properties different
from a glass substrate, and they show very weak chemical resistance
to a variety of chemical products including various solvents. In
order to fabricate a highly functional plastic substrate, the
substrate surface must be protected with a substance which exhibits
very low moisture and oxygen transmission rates and a high
resistance to various chemicals. Further, in order for the plastic
substrate to block moisture and oxygen transmission, the thermal
stress between the plastic substrate and the ceramic passivation
layer must be reduced, and microparticles have to adhere and
accumulate on the substrate surface while reducing the surface
roughness of the substrate. In order to achieve the above
objective, there is a need to develop a passivation multilayer
technique of repeatedly laminating an organic material capable of
being planarized and a ceramic inorganic material having strong
protective properties.
[0007] The present inventors have thus endeavored to overcome the
problems in the prior art and develop an organic/inorganic hybrid
thin film passivation layer. The hybrid thin film passivation layer
includes an organic polymer passivation layer made of a
photocurable polymer according to a UV/ozone (O.sub.3) curing
process which is capable of improving surface energy and forming a
more delicate surface structure compared to that made by a
conventional UV curing process, and an inorganic thin film
passivation layer prepared by using a nanocomposite material mixed
with two or more inorganic materials in an up-and-down laminated
structure. The organic/inorganic hybrid thin film passivation layer
of the present invention can effectively block oxygen and moisture
transmission, ensuring the stability and reliability of a device
and improve the gas barrier property of a plastic substrate.
SUMMARY OF THE INVENTION
[0008] The primary objective of the present invention is to provide
an organic/inorganic hybrid thin film passivation layer capable of
effectively blocking oxygen and moisture transmission, to ensure
the stability and reliability of a device fabricated on a substrate
and improve the gas barrier property of a plastic substrate, as
well as a fabrication method thereof.
[0009] In accordance with one embodiment of the present invention,
there is provided an organic/inorganic hybrid thin film passivation
layer for blocking oxygen and moisture transmission of an organic
electronic device fabricated on a substrate and improving the gas
barrier property of a plastic substrate. The hybrid thin film
passivation layer includes an organic polymer passivation layer
made of a photocurable polymer according to a UV/ozone curing
process and an inorganic thin film passivation layer prepared by
using a nanocomposite material containing at least two inorganic
materials, and has an up-and-down laminated structure of the
organic polymer passivation layer and inorganic thin film
passivation layer.
[0010] In accordance with another embodiment of the present
invention, a method of fabricating an organic/inorganic hybrid thin
film passivation layer having the above characteristics by a
UV/ozone curing process is provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The embodiments of the present invention will be described
in detail with reference to the following drawings.
[0012] FIG. 1 is a schematic diagram illustrating the structure of
a prior art organic electronic device sealed with a metal cap.
[0013] FIG. 2 is a schematic diagram illustrating the structure of
a prior art organic electronic device on which an inorganic
composite thin film is deposited as a passivation layer.
[0014] FIG. 3 is a schematic diagram illustrating the structure of
an organic electronic device fabricated on a substrate to which an
organic/inorganic hybrid thin film passivation layer according to
the present invention is applied.
[0015] FIG. 4 is a schematic diagram illustrating the structure of
a plastic substrate to which an organic/inorganic hybrid thin film
passivation layer according to the present invention is
applied.
[0016] FIG. 5 is a schematic diagram illustrating the structure of
a plastic substrate where an organic/inorganic hybrid thin film
passivation layer prepared by a UV/ozone curing process according
to the present invention is applied to both the top and bottom of
the substrate.
[0017] FIG. 6 is a schematic diagram illustrating the structure of
a plastic substrate to which an organic/inorganic hybrid thin film
passivation layer prepared by a UV/ozone curing process according
to the present invention is repeatedly applied to result in a
multilayer structure.
[0018] FIGS. 7(a)-(d) show scanning electron microscope (SEM)
photographs of the cross-sections and surfaces of the
organic/inorganic hybrid thin film passivation layer according to
the present invention. FIG. 7(a) shows the surface of a MS-31
inorganic thin film passivation layer, while FIG. 7(b) shows the
surface of an acrylate resin organic polymer passivation layer.
FIG. 7(c) shows the cross-section of an inorganic/organic hybrid
thin film passivation layer, while FIG. 7(d) shows the
cross-section of an organic/inorganic hybrid thin film passivation
layer.
[0019] FIG. 8 is a graph showing the UV-visible light transmission
rate of an organic/inorganic hybrid thin film passivation layer
prepared by a UV/ozone curing process according to the present
invention.
[0020] FIGS. 9(a)-(d) show atomic force microscope (AFM)
photographs of surface planarization of an organic polymer
passivation layer when a photocurable polymer undergoes a UV curing
process for 1.5 min (FIG. 9(a)), a UV/ozone curing treatment for
1.5 min (FIG. 9(b)), a UV/ozone curing treatment for 3 min (FIG.
9(c)), and a UV/ozone curing treatment for 5 min (FIG. 9(d))
according to the present invention.
[0021] FIG. 10 is a graph showing the change in surface contact
angles of an organic polymer passivation layer when a photocurable
polymer undergoes UV/ozone curing according to the present
invention for different lengths of time.
[0022] FIG. 11 is a graph comparing the moisture transmission rates
of an organic polymer passivation layer prepared by a UV/ozone
curing process according to the present invention to those of that
prepared by a conventional UV curing process.
[0023] FIGS. 12a and 12b are graphs showing the moisture
transmission rates of an organic/inorganic hybrid thin film
passivation layer according to the present invention, on which an
organic polymer passivation layer and an inorganic thin film
passivation layer are repeatedly laminated in a three-layer
structure and a six-layer structure, respectively.
DETAILED DESCRIPTION OF THE INVENTION
[0024] The organic/inorganic hybrid thin film passivation layer
according to the present invention is characterized as including an
organic polymer passivation layer made of a photocurable polymer
according to a UV/ozone curing process and an inorganic thin film
passivation layer prepared by using a nanocomposite material
containing at least two inorganic materials and having a
up-and-down laminated structure of the organic polymer passivation
layer and inorganic thin film passivation layer.
[0025] In particular, the organic/inorganic hybrid thin film
passivation layer according to the present invention may be
fabricated by the following steps: [0026] 1) coating an organic
electronic device fabricated on a substrate or the top or both the
top and bottom of a plastic substrate with a photocurable polymer;
[0027] 2) curing the coated photocurable polymer by UV/ozone
(UV/O.sub.3) irradiation to form an organic polymer passivation
layer; and [0028] 3) depositing a nanocomposite material containing
at least two inorganic materials on the organic polymer passivation
layer to form an inorganic thin film passivation layer.
[0029] Step 1) above is for securing the stability and reliability
of an organic electronic device fabricated on a substrate and for
improving the gas barrier property of a plastic substrate by
effectively blocking moisture and oxygen transmission through the
formation of a passivation layer. In step 1), a photocurable
polymer is coated on the surface of the organic electronic device
fabricated on a substrate or on the top or both the top and bottom
of a plastic substrate. The application of the photocurable polymer
in the present invention is carried out by using conventional
methods in the art, such as spin coating, screen printing, bar
coating, inkjet printing, dipping and the like. In some embodiments
of the present invention, the photocurable polymer may be applied
to the organic electronic device fabricated on the substrate or the
plastic substrate to the extent that it covers the top or both the
top and bottom of the substrate. In certain embodiments, the
photocurable polymer may be coated to have an average thickness of
about 0.1 to about 10 .mu.m.
[0030] Any type of photocurable polymer may be used in the present
invention, as long as it can be cured by light (UV) irradiation.
Suitable photocurable polymers may include, but are not limited to,
epoxy resins, acrylate resins, thermal curable polyimide,
polyethylene, and the like.
[0031] Suitable substrates to which the organic/inorganic hybrid
thin film passivation layer is applied according to the present
invention include, but are not limited to, a flexible substrate and
a glass substrate. Examples of the flexible substrate may include
polyethylene terephthalate (PET), polymethyl methacrylate (PMMA),
polycarbonate (PC), polyethylene sulfone (PES) and the like. The
organic electronic devices fabricated on such substrates can be of
any kind, so long as they are composed of conventional organic
materials well known in the art. Representative examples of such
organic electronic devices may include OLED, OTFT, solar cells,
other devices containing organic materials as a major component,
and the like.
[0032] Suitable plastic substrates for use in the present invention
may include any substrate made of polymer materials widely used as
a display substrate, such as polyethersulfone, polycarbonate,
polyethylene terephthalate, polyimide and the like. Further, any
kind of plastic substrate, if it is conventionally used in the art,
may be used in the present invention without limitation. Among
various plastic substrates, however, polyethersulfone substrates
have the advantage of high transparency.
[0033] Step 2) above is for forming an organic polymer passivation
layer by curing the photocurable polymer coated on the surface of
the organic electronic device fabricated on the substrate or on the
top or both the top and bottom of the plastic substrate with
UV/ozone (UV/O.sub.3) irradiation having a short wavelength.
[0034] The UV/ozone curing process of step 2) consists of
pre-curing, UV/ozone irradiation, and heat curing. First, the
photocurable polymer coated in step 1) is subjected to pre-curing
by using a hot plate or an oven at a temperature of 70 to
90.quadrature. for 2 to 5 min so that the additives and/or
impurities included in the photocurable polymer, such as acrylate
resin, are gradually removed. Then, the pre-cured photocurable
polymer is irradiated with UV/ozone to carry out a light curing
process. During the light curing process by a UV/ozone irradiation,
oxygen (O.sub.2) molecules are degraded into an atomic state by
irradiating the photocurable polymer with a light source having a
wavelength of 170 to 200 nm for 1 to 7 min, followed by irradiation
of the generated oxygen atoms with a light source having a
wavelength 240 to 260 nm for 1 to 7 min, resulting in ozone
generation. The major wavelength of the light source which directly
influences the curing efficiency is in the range of from 240 to 260
nm, and the irradiated light source energy is in the range of from
2400 to 3000 mJ/cm.sup.2. Finally, the photocurable polymer is
subjected to heat curing by using an oven at a temperature of 100
to 120.quadrature. for 1 to 2 hr, thereby forming an organic
polymer passivation layer. The UV/ozone curing process as described
above can significantly increase the hardness of an organic polymer
passivation layer, as compared with a curing process that uses only
UV, and remarkably improve its function as a passivation layer
through an increase in interfacial adhesion strength.
[0035] In certain embodiments of the present invention, the coated
photocurable polymer from step 1) is subjected to pre-curing by
using a hot plate at 80.quadrature. for 3 min, followed by
irradiation with a light source having a wavelength of 184.9 nm for
5 min to degrade oxygen (O.sub.2) molecules into oxygen atoms.
Then, in order to generate ozone from the oxygen atoms, a UV/ozone
curing process is carried out by irradiating with a light source
having a wavelength of 253.7 nm for 5 min. The major wavelength of
the light source which directly influences the curing efficiency is
253.7 nm, and the irradiated light source energy is 2800
mJ/cm.sup.2. After the UV/ozone curing process is completed, the
photocurable polymer is finally subjected to heat curing by using
an oven at 120.quadrature. for 2 hr, which results in the formation
of an organic polymer passivation layer.
[0036] Step 3) above is for depositing a nanocomposite material
containing at least two inorganic materials on the organic polymer
passivation layer formed in step 2) so as to form an inorganic thin
film passivation layer.
[0037] In the above step, an organic/inorganic hybrid thin film
passivation layer according to the present invention is fabricated
by depositing a nanocomposite material containing at least two
inorganic materials on the organic polymer passivation layer formed
on the surface of an organic electronic device fabricated on a
flexible substrate or a glass substrate, or on the top or both the
top and bottom of a plastic substrate by using an electron beam
evaporator, a sputter, a physical vapor deposition (PVD), a
chemical vapor deposition (CVD), an atomic layer deposition (ALD)
and the like, resulting in the formation of an inorganic thin film
passivation layer. The inorganic thin film passivation layer may be
deposited to have an average thickness of, for example, 0.1 to 0.5
.mu.m.
[0038] The nanocomposite material used in the present invention is
a mixture containing at least two inorganic materials selected from
the group consisting of metal oxides, non-metal oxides, nitrides
and salts, e.g., aluminum oxides (e.g., Al.sub.2O.sub.3), silicone
oxides (e.g., SiO.sub.2), silicone nitrides (e.g., SiNx), silicone
oxidenitrides (e.g., SiON), magnesium oxides (e.g., MgO), indium
oxides (e.g., In.sub.2O.sub.3), magnesium fluorides (e.g.,
MgF.sub.2), and the like.
[0039] The inorganic thin film passivation layer formed in the
above step can improve the resistance properties against moisture
and oxygen by blocking the paths for moisture and oxygen
transmission which can be generated by defects (e.g., pinholes,
grain boundaries and cracks) on the organic polymer passivation
layer formed in steps 1) and 2).
[0040] An organic/inorganic hybrid thin film passivation layer
having a multi-layer laminate structure repeatedly including more
than one pair of the organic polymer passivation layer and
inorganic thin film passivation layer may be fabricated by
depositing the organic polymer passivation layer and inorganic thin
film passivation layer one by one repeatedly. Further, it is also
possible to carry out step 3) before steps 1) and 2) by first
forming an inorganic thin film passivation layer on the surface of
the organic electronic device fabricated on the flexible substrate
or the glass substrate, or on the top or both the top and bottom of
a plastic substrate, followed by depositing an organic polymer
passivation layer thereon, to thereby fabricate an
inorganic/organic hybrid thin film passivation layer.
Alternatively, more than one pair of the inorganic thin film
passivation layer and organic polymer passivation layer prepared in
the above order can be laminated repeatedly to fabricate an
inorganic/organic hybrid thin film passivation layer having a
multi-layer laminate structure.
[0041] As described above, the organic/inorganic hybrid thin film
passivation layer in accordance with the present invention may have
a structure where the order in which the organic polymer
passivation layer and inorganic thin film passivation layer is
laminated is reversed or a structure where more than one pair of
the organic polymer passivation layer and inorganic thin film
passivation layer is laminated in a multi-layer structure, both of
which being capable of effectively blocking moisture and oxygen
transmission.
[0042] The method of fabricating an organic/inorganic hybrid thin
film passivation layer according to the present invention has the
following characteristics.
[0043] First, the method in accordance with the present invention
uses a UV/ozone curing process to form an organic polymer
passivation layer which is capable of blocking moisture and oxygen
transmission more efficiently than that prepared by conventional UV
curing processes. The UV/ozone curing process can increase the
surface energy of the organic polymer passivation layer and induce
the surface to become hydrophilic, leading to an enhancement of
adhesion strength between the organic polymer passivation layer and
the upper passivation layer. Further, the method of the present
invention enables the formation of passivation layers having a
larger area than the area of the respective organic electronic
device and repetitive passivation layers as well as passivation
layers covering the overall surface thereof, resulting in the
effective blocking of the transmission channels of moisture and
oxygen that may penetrate into a large area organic light emitting
device in a perpendicular and/or a horizontal direction. Therefore,
the method of the present invention can improve the stability and
reliability of the device.
[0044] Second, the organic polymer passivation layer, whose surface
has become hydrophilic by the UV/ozone curing process, shows high
moisture-absorbing properties and is capable of absorbing any
residual moisture to its surface, thereby minimizing damages to the
device due to moisture transmission.
[0045] Third, the organic polymer passivation layer prepared by the
UV/ozone curing process of the present invention exhibits a strong
crosslinking effect and is capable of blocking the transmission
channels of moisture and oxygen that may penetrate in a
perpendicular direction and efficiently lowering moisture and
oxygen transmission.
[0046] Fourth, the method of the present invention can fabricate an
organic/inorganic hybrid thin film passivation layer capable of
efficiently blocking moisture and oxygen transmission by depositing
an inorganic thin film passivation layer made of a nanocomposite
material containing at least two inorganic materials on the organic
polymer passivation layer prepared above.
[0047] The organic/inorganic hybrid thin film passivation layer in
accordance with the present invention having the characteristics
described above can effectively block moisture and oxygen
transmission, and is thus useful for securing the stability and
reliability of the organic electronic device and improving the gas
barrier property of the plastic substrate.
[0048] Hereinafter, the characteristics of the organic/inorganic
hybrid thin film passivation layer according to the present
invention will be explained in more detail with reference to the
accompanying drawings.
[0049] FIG. 3 is a schematic diagram illustrating the structure of
an organic electronic device fabricated on a substrate to which an
organic/inorganic hybrid thin film passivation layer 100 according
to the present invention is applied. The overall surface of the
organic light emitting device includes an anode glass substrate 1,
a hole injection layer 2, a hole transfer layer 3, a light emitting
layer 4, an electron transfer layer 5, an electron injection layer
6 and a cathode electrode 7, and is covered with an organic polymer
passivation layer 10 and an inorganic thin film passivation layer
11. Here, the organic polymer passivation layer 10 is formed by
using acrylate resin as a photocurable polymer, and the inorganic
thin film passivation layer 11 is deposited thereon by using a
nanocomposite material in which magnesium oxide and silicone oxide
are mixed in an appropriate ratio, for example, MS-31
(MgO:SiO.sub.2=3:1 wt %). The organic/inorganic hybrid thin film
passivation layer 100 applied to the organic light emitting device
can complement the mutual defects between the organic polymer
passivation layer 10 and inorganic thin film passivation layer 11,
and thereby, effectively block moisture and oxygen
transmission.
[0050] FIG. 4 is a schematic diagram illustrating the structure of
a plastic substrate 12 to which the organic/inorganic hybrid thin
film passivation layer 100 according to the present invention is
applied, while FIG. 5 is a schematic diagram illustrating the
structure of a plastic substrate 12 where the organic/inorganic
hybrid thin film passivation layer 100 prepared by a UV/ozone
curing process according to the present invention is applied to
both the top and bottom of the substrate. The organic/inorganic
hybrid thin film passivation layer 100 applied to the plastic
substrate 12 can effectively block moisture and oxygen
transmission, and thereby further improve the gas barrier
property.
[0051] FIG. 6 is a schematic diagram illustrating the structure of
a plastic substrate 12 to which an organic/inorganic hybrid thin
film passivation layer 100 prepared by the UV/ozone curing process
according to the present invention is repeatedly applied to result
in a multilayer structure. The plastic substrate exhibits a
superior effect in blocking moisture and oxygen transmission and an
improved gas barrier property.
[0052] FIGS. 7(a)-(d) are scanning electron microscope (SEM)
photographs of the cross-sections and surfaces of the
organic/inorganic hybrid thin film passivation layer according to
the present invention. FIG. 7(a) shows the surface of an inorganic
thin film passivation layer in the organic/inorganic hybrid thin
film passivation layer according to the present invention,
confirming that the inorganic thin film passivation layer is in a
high amorphous state where there are almost no grains serving as
channels for transmission of moisture and oxygen. FIG. 7(b) shows
the surface of an organic polymer passivation layer in the
organic/inorganic hybrid thin film passivation layer according to
the present invention, demonstrating that pinholes or pores are not
formed on the surface thereof and that the organic polymer
passivation layer is uniformly coated on a substrate. FIG. 7(c)
shows the cross-section of the organic/inorganic hybrid thin film
passivation layer according to the present invention which has a
structure of an inorganic thin film passivation layer formed on a
substrate and an organic polymer passivation layer deposited
thereon. In contrast to FIG. 7(c), FIG. 7(d) shows the
cross-section of a structure of an organic polymer passivation
layer formed on a substrate and an inorganic thin film passivation
layer deposited thereon. Although both the organic polymer
passivation layer and inorganic thin film passivation layer are
heterogeneous thin film materials, they are found to be fabricated
in a very close-packed form due to the strong interfacial adhesion
strength between them.
[0053] The adhesion strengths between the interfaces of the
organic/inorganic hybrid thin film passivation layer prepared by
the UV/ozone curing process according to the present invention are
measured according to the method described in ASTM 3359-93B and
compared with the adhesion strength of a conventional hybrid thin
film passivation layer prepared by a UV curing process. The results
are shown in Table 1 below.
TABLE-US-00001 TABLE 1 Upper layer material Lower layer Acrylate
resin Acrylate resin material MS-31 cured by UV cured by UV/O.sub.3
Glass 92% 3% 4% PES 98% 65% 96% ITO 71% 2% 3% MS-31 x 7% 37%
Acrylate resin 93% x x cured by UV Acrylate resin 98% x x cured by
UV/O.sub.3
[0054] As shown in Table 1, the organic/inorganic hybrid thin film
passivation layer prepared by the UV/ozone curing process of the
present invention exhibits higher adhesion strength between the
passivation layer interfaces than that prepared by the conventional
UV curing process, and those unique characteristics are found to
effectively block moisture and oxygen that may penetrate from a
perpendicular and horizontal directions.
[0055] FIG. 8 is a graph showing the UV-visible light transmission
rate of each constituent of the organic/inorganic hybrid thin film
passivation layer according to the present invention. As shown in
FIG. 8, the light transmission rate of each constituent is 80% or
more, which suggests that the organic/inorganic hybrid thin film
passivation layer of the present invention can be effectively used
as a passivation layer for a top emissive type organic light
emitting device.
[0056] FIGS. 9(a)-(d) show atomic force microscope (AFM)
photographs of the surface planarization of the organic polymer
passivation layer when the photocurable polymer undergoes a
UV/ozone curing process for different amounts of time. The UV/ozone
apparatus used herein exhibits an etching speed of 5 nm/min for an
organic material, leading to surface planarization caused by a
difference in relative etching speeds between surfaces at higher
and lower altitudes in the polymer thin film. As shown in FIGS.
9(a)-(d), in a conventional UV curing process, the mean roughness
was 3.244 nm (FIG. 9(a)), but after undergoing the UV/ozone process
for 1.5 min (FIG. 9(b)), 3 min (FIG. 9(c)) and 5 min (FIG. 9(d)),
the mean roughness is improved to 1.149 nm. The improved surface
roughness of the organic polymer passivation layer makes it
possible to fabricate a passivation layer having a uniform thin
film thickness as shown in FIG. 6 when fabricating a passivation
layer in a multilayer structure, and can improve the light
transmission by minimizing light scattering at the interface.
[0057] FIG. 10 is a graph showing the change in surface contact
angles of an organic polymer passivation layer depending on the
length of the UV/ozone curing time. As shown in FIG. 10, compared
to the conventional UV curing process, the UV/ozone curing process
of the present invention is found to convert a hydrophobic surface
into a hydrophilic one within a short time. A decrease in contact
angle in the conventional UV curing process occurs because a very
small amount of ozone generated during the UV irradiation forms a
number of hydrophilic groups at the surface. However, the number of
the hydrophilic groups is too small to induce a drastic change in
surface polarity. On the other hand, in the UV/ozone curing process
according to the present invention, the lamp installed in the
UV/ozone apparatus has high energy due to a short wavelength and
can thus break the molecular binding, thereby generating a large
amount of ozone within the first 3 to 5 sec. The amount of ozone
thus generated is much more than that generated by a single
irradiation with UV, and since the ozone and UV generated in the
apparatus are cured, the surface polarity was found to change into
hydrophilic despite the short-time curing. The above converted
surface of the organic polymer passivation layer can enhance the
adhesion strength between the upper and lower interfaces and
improve surface roughness, as mentioned above.
[0058] FIG. 11 is a graph comparing the moisture transmission rates
of an acrylate polymer passivation layer cured by UV/ozone and an
organic/inorganic hybrid thin film passivation layer comprising the
same with an acrylate polymer passivation layer cured by UV and an
organic/inorganic hybrid thin film passivation layer comprising the
same. As a result, it has been found that when using the UV/ozone
curing process according to the present invention instead of the
conventional UV curing process, the moisture resistance of the
organic/inorganic hybrid thin film passivation layer, as well as
the single acrylate passivation layer, is significantly increased.
This suggests that the organic/inorganic hybrid thin film
passivation layer in accordance with the present invention can be
effectively applied to a flexible organic light emitting
device.
[0059] FIGS. 12a and 12b are graphs showing the moisture
transmission rates of organic/inorganic hybrid thin film
passivation layers having a structure where an organic polymer
passivation layer prepared by a UV/ozone curing process and an
inorganic thin film passivation layer containing a nanocomposite
material are repeatedly laminated. FIG. 12a depicts the moisture
transmission rate of the organic/inorganic hybrid thin film
passivation layer in a three-layer laminate structure, and FIG. 12b
depicts the moisture transmission rate of the organic/inorganic
hybrid thin film passivation layer in a six-layer laminate
structure. As such, it has been found that the organic/inorganic
hybrid thin film passivation layer having such a multilayer
laminate structure exhibits a significantly reduced moisture
transmission rate, as compared with that having a two-layer
laminate structure as shown in FIG. 11, and thereby exhibits a
superior effect in blocking moisture transmission. In particular,
while the organic/inorganic hybrid thin film passivation layer
having a two-layer laminate structure exhibits a moisture
transmission rate of 10.sup.-3, the organic/inorganic hybrid thin
film passivation layer having a multilayer laminate structure
exhibits a moisture transmission rate of 10.sup.-4 in case of a
three-layer structure and that of 10.sup.-6 in case of a six-layer
structure, demonstrating that the multi-layer laminate structure is
more efficient in blocking moisture and oxygen transmission. These
results suggest that when an organic/inorganic hybrid thin film
passivation layer is fabricated by mixing an acrylate polymer
material with a nanocomposite material having low moisture and
oxygen transmission rates, a superior effect in blocking moisture
and oxygen transmission can be expected and that such an effect can
be further enhanced by the repetitive lamination of an
organic/inorganic hybrid thin film passivation layer.
[0060] As described above, since the present invention provides a
method of fabricating an organic/inorganic hybrid thin film
passivation layer in a multilayer laminate structure including an
organic polymer passivation layer prepared by a UV/ozone curing
process using a short-wavelength light source, it is possible to
form a closely packed thin film and improve the adhesion strength
between the thin film interfaces, resulting in a significant
enhancement in the resistance against moisture and oxygen
transmission. Further, the UV/ozone curing process according to the
present invention allows the surface planarization of the organic
polymer passivation layer, thereby improving the resistance
uniformity against moisture and oxygen transmission depending on
the position of thus manufactured passivation layer and enhancing
light transmission by minimizing surface light scattering.
Therefore, if the organic/inorganic hybrid thin film passivation
layer according to the present invention is used for the
fabrication of a passivation layer of an organic electronic device,
it can efficiently protect an organic layer of the device from
moisture and oxygen, and thereby significantly contribute to the
stability and reliability of the device. Further, the
organic/inorganic hybrid thin film passivation layer according to
the present invention can be effectively used for a plastic
substrate so as to provide excellent gas barrier property.
[0061] While the present invention has been described and
illustrated with respect to a preferred embodiment of the
invention, it will be apparent to those skilled in the art that
variations and modifications are possible without deviating from
the broad principles and teachings of the present invention, which
should be limited solely by the scope of the claims appended
hereto.
* * * * *